Precision casting titanium aluminide

Abstract

A titanium aluminide is composed of 31.5 to 33.5 weight % of Al, 1.5 to 2.3 weight % of Fe, 1.5 to 2.1 and 3.7 to 4.8 weight % of Nb, 0.07 to 0.12 weight % of B with remainder being Ti and inevitable impurities. The 1.5-2.0 weight % of Nb may be replaced with 0.5 to 2.0 weight % of V if severe oxidation resistance is not necessary. The titanium aluminide is melted and poured into a mold, and the melt is cooled in the mold naturally.

I claim: 
     
       1. A method of precision casting an article, comprising the steps of: (A) preparing a titanium aluminide including by weight 31.5-33.5% of Al, 1.5-2.3% of Fe, one of 1.5-2.1% Nb and 3.7-4.8% Nb and 0.07-0.12% of B with the remainder being Ti and inevitable impurities;   (B) melting the titanium aluminide;   (C) pouring the melt into a mold; and   (D) cooling the melt in the mold such that the melt temperature is lowered to about 800°-1,000° C. in about 20 minutes, whereby beta phase is precipitated around gamma particles and coarse lamellar particles are not produced.   
     
     
       2. The method of claim 1, wherein step (B) includes heating the titanium aluminide to 1500° C. or more. 
     
     
       3. The method of claim 2, further including the step of preheating the mold to about 400°-600° C. prior to step (C). 
     
     
       4. The method of claim 3, wherein the mold is a mold for casting a thin and complex shape product. 
     
     
       5. A method of precision casting an article, comprising the steps of: (A) preparing a titanium aluminide including by weight 31.5-33.5% of Al, 1.5-2.3% of Fe, 1.5-2.0% of V and 0.07-0.12% of B with the remainder being Ti and inevitable impurities,   (B) melting the titanium aluminide;   (C) pouring the melt into a mold; and   (D) cooling the melt in the mold such that the melt temperature is lowered to about 800°-1,000° C. in about 20 minutes, whereby beta phase is precipitated around gamma particles and coarse lamellar particles are not produced.   
     
     
       6. The method of claim 5, wherein step (B) includes heating the titanium aluminide to 1500° C. or more. 
     
     
       7. The method of claim 6, further including the step of preheating the mold at about 400°-600° C. prior to step (C). 
     
     
       8. The method of claim 7, wherein the mold is a mold for casting a thin and complex shape product. 
     
     
       9. A method of precision casting an article, comprising the steps of: (A) preparing a titanium aluminide including by weight 31.5-33.5% of Al, 1.5-2.3% of Fe, one of 1.5-2.1% of Nb and 3.7-4.8% Nb, and 0.07-0.12% of B with the remainder being Ti and inevitable impurities;   (B) melting the titanium aluminide;   (C) pouring the melt into a mold; and   (D) cooling the melt in the mold at a cooling rate to cause the beta phase to be precipitated around gamma particles in the article and prevent the generation of coarse lamellar particles in the article.   
     
     
       10. The method of claim 9, wherein the step (D) is carried out such that the melt temperature is lowered to 800°-1000° C. in about 20 minutes. 
     
     
       11. The method of claim 9, wherein the step (B) includes heating the titanium aluminide to 1500° C. or more. 
     
     
       12. The method of claim 9, further including the step of preheating the mold to about 400°-600° C. prior to the step (C). 
     
     
       13. A method of precision casting an article, comprising the steps of: (A) preparing a titanium aluminide including by weight 31.5-33.5% of Al, 1.5-2.3% of Fe, 1.5-2.0% of V and 0.07-0.12% of B with the remainder being Ti and inevitable impurities;   (B) melting the titanium aluminide;   (C) pouring the melt into a mold; and   (D) cooling the melt in the mold at a cooling rate to cause the beta phase to be precipitated around gamma particles in the article and prevent the generation of coarse lamellar particles in the article.   
     
     
       14. The method of claim 13, wherein the step (D) is carried out such that the melt temperature is lowered to 800°-1000° C. in about 20 minutes. 
     
     
       15. The method of claim 13, wherein the step (B) includes heating the titanium aluminide to 1500° C. or more. 
     
     
       16. The method of claim 13, further including the step of preheating the mold to about 400°-600° C. prior to the step (C).